It is complicated or even almost impossible to build classic wide-band array antennas providing good angle resolution. The reason for this is that the separation of the elements is set by the highest frequency, typically half a wavelength at fmax. The physical size of the elements is set by the lowest frequency, typically half a wavelength at fmin. Thus, there is apparently a contradiction between obtaining a wide bandwidth of the antenna and the array density needed to avoid grating lobes at large scan angles.
Another problem is that array antennas having a large number of elements will be undesired complex and expensive. Furthermore rotating antennas are generally undesired as that implies further mechanical complexity. From a strategic point of view there is also a desire to be able to keep peak power as low as possible to minimize the risk of being detected.
Typical solutions of today utilize fully filled arrays and rotating antennas combined with range coded long pulses, for instance using a binary phase code. Signal classification is difficult with present solutions and different hardware solutions have to be used for a respective function category, for instance, a radar function or a jamming function.
Therefore there is a demand for further improvements of wide-band arrays for obtaining also a better angular resolution produced by a less complex solution compared to the state of the art.